Positive displacement fluid measurement systems may be used to measure a flow rate or volume of a fluid or gas. For example, dispensing systems may use feedback from a positive displacement fluid meter to control the volume of fluid dispensed. Such control systems are often used in lieu of time-on controls to more accurately dispense precise amounts of fluid or gas and is commonly used in a variety of settings including, but not limited to, the industrial, healthcare, pharmaceutical and food and beverage industries. For example, a positive displacement fluid meter may be used in the manufacturing process of a drug which requires accurate measurement of two materials to be mixed into a single batch. The positive displacement fluid meter may be installed in the supply lines of the respective materials and feedback from the meters may be used to dispense the appropriate amount of each material into a blend tank to be mixed. This application of a positive displacement meter, like many others, may require the positive displacement meter to have an accuracy of measurement (e.g., +/−0.5%) to comply with quality control or regulations, for example. Accordingly, a positive displacement meter that accurately measures a volume of fluid or gas can help facilitate performing intended function of a fluid dispensing system or process.
An example fluid flow meter is described in the commonly-assigned application, U.S. Pat. No. 9,383,235, assigned to Ecolab Inc., St. Paul, Minn., the disclosure of which is hereby incorporated by reference. Manufacturers typically provide a factory calibration which correlates the volume of a pocket of fluid to a rotational count corresponding to rotation of one or more components (e.g., oval gears) in the flow meter for various volumes of flows. Thus, by counting the number of pulses produced by the fluid flow meter, the volume flow rate can be determined based on the factory calibration.
Such factory calibration may not be accurate outside of a flow range. For instance, at low flow rates near the flow minimum, the flow meter may not produce any input pulses, but may still have flow through various mechanical components of the flow meter. Similar issues may occur at operation near the flow maximum. Accordingly, manufacturers specify a range over which the flow meter's calibration is reliable. However, doing so may be restrictive to an end user who may intend to use flow meters for measuring flow over a wide range.